1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
|
module day_04_utils
implicit none
contains
recursive function find_xmas(arr, row, col,row_dir, col_dir, search_letter) result(found)
implicit none
character(len=140), intent(in), allocatable :: arr(:)
character(len=1), intent(in) :: search_letter
integer, intent(in) :: row, col, row_dir, col_dir
integer :: new_row, new_col
logical :: found
if(arr(row)(col:col) == search_letter) then
if(search_letter == 'S') then
found = .true.
else
new_row = row + row_dir
new_col = col + col_dir
if(new_row > len(arr(row)) .or. new_row < 1 .or. new_col > size(arr) .or. new_col < 1) then
found = .false.
else
select case(search_letter)
case('M')
found = find_xmas(arr, new_row, new_col, row_dir, col_dir, 'A')
case('A')
found = find_xmas(arr, new_row, new_col, row_dir, col_dir, 'S')
end select
end if
end if
else
found = .false.
end if
end function find_xmas
end module day_04_utils
program day_04
use day_04_utils
implicit none
character(len=140) , allocatable :: lines(:)
integer :: io, row, col, score, z
logical :: found
score = 0
open(newunit=io, file='./day_04_input.txt', status='old', action='read')
allocate(lines(140))
read(io, '(a)') lines
do row = 1, size(lines)
do col = 1, len(lines(row))
if (lines(row)(col:col) == 'X') then
do z = 1, 8
found = .false.
select case (z)
case(1)
found = find_xmas(lines, row, col-1, 0, -1, 'M')
case(2)
found = find_xmas(lines, row-1, col-1, -1, -1, 'M')
case(3)
found = find_xmas(lines, row-1, col, -1, 0, 'M')
case(4)
found = find_xmas(lines, row-1, col+1, -1, 1, 'M')
case(5)
found = find_xmas(lines, row, col+1, 0, 1, 'M')
case(6)
found = find_xmas(lines, row+1, col+1, 1, 1, 'M')
case(7)
found = find_xmas(lines, row+1, col, 1, 0, 'M')
case(8)
found = find_xmas(lines, row+1, col-1, 1, -1, 'M')
end select
if(found) then
score = score + 1
end if
end do
end if
end do
end do
deallocate(lines)
print*, score
end program day_04
|
